High idle not going away
 

Hey, 87 base NA, a little exhaust work, anyway my idle is high as heck. I've had this issue since I got my car, after startup with or without accelerated warm up, my idle is about 1500 RPMs. I've adjusted my idle screw, and it seems like nothing changed when I did that. Also, when I'm idling, my exhaust is very rich.

I'm thinking my problem is a vacuum leak, but I'm not exactly sure, or how to test for it. I also don't know if my O2 sensor is connected, where should that be located? I have a feeling that may help my richness.

my 89 gtu n/a did the same thing when i bought it. i checked the idle screw, set tps, vacuum leaks, and everything. come to find out it was my BAC valve. it's located right under where the intake pipe connects to the throttle body. See if that's it. if your still burning rich after that then scan for error codes.

spray some carb cleaner around your intake, if the idle drops that is where a leak is. I would check your tps! oh and make sure there is a little play in the throttle cable.

Umm... no Carb cleaner is FLAMABLE!!!! your idle will go higher when you hit a vacuum leak.

to me it sounds like if your idle is steady at ~1500 you should chack the fast idle cam on the back side of your TB. there is a coolant thermowax pellet back there too that does go bad after a while. your car may just be stuck in cold start mode.

I had the same problem 1500 idle on my T2, i did RETed's TB mod from his website FC3SPro.com and everything is PERFECT now i have an 800rpm idle and better throttle response.

hope this helps,
TR

02 is disabled at idle.

The fast idle cam/screw/thermowax is almost impossible to work on on a 87 non turbo, unless you remove the throttle and work with it on the bench IMHO.

It's not impossible that the BAC is stuck. I've seen that once on my cars. Clean with carb cleaner and do not pry on the diaphram inside at all. With the key to ON, the bac should be clicking/vibrating. If you remove it from the intake and leave the elec plug on, you should be able to spray and dump cleaner inside while the bac is vibrating/agitating.

I use Starter Fluid when suspecting vacuum leaks. I have all my arm hairs and eyebrows. I find it more satisfactory than carb cleaner.

does the BAC thing cause your idle to jump around and drop ramdomly? I've checked my timing, tps, sprayed with quick start. no vaccume leaks that i found. Is the BAC the thing on the UIM with the coolant line running to/from it with the white plug on the front/ bottom?
S5 N/A BTW

yes that is where the BAC is located. there is two nuts to remove which is center top and center bottom. once removed also make sure that the seal on it is still good.

I'm with him, check the bac. Could even just be a bad contact. I had a bad connector at the bac valve and my idle used to vary. I would say it's either the bac or the thermowax. Just close the throttle plates with the car warmed up and if your idle drops to normal than there's something wrong with the thermowax or the fast idle cam. Like they said, you can't work on the fast idle on the car, it will require removing the intakes. Good luck.

Brent